Splash can now return requests/responses information in HAR format. See
render.har endpoint and har argument of render.json
endpoint. A simpler history argument is also available.
With HAR support it is possible to get timings for various events,
HTTP status code of the responses, HTTP headers, redirect chains, etc.

Processing of related resources is stopped earlier and more robustly
in case of timeouts.

wait parameter changed its meaning: waiting now restarts
after each redirect.

Dockerfile is improved: image is updated to Ubuntu 14.04;
logs are shown immediately; it becomes possible to pass additional
options to Splash and customize proxy/js/filter profiles; adblock filters
are supported in Docker; versions of Python dependencies are pinned;
Splash is started directly (without supervisord).

Splash now tries to start Xvfb automatically - no need for xvfb-run.
This feature requires xvfbwrapper Python package to be installed.